In order to prevent the issue or the leakage of data, an HDD (Hard disk drive) with an authentication function is known. For the authentication function, the authentication is carried out before the write in from a machine to the HDD, and the HDD can be accessed only in the condition that the machine succeeds in the authentication. If the authentication fails or the data in the HDD will be read out in the condition that the authentication is not carried out, an encryption key for a data password stored in the HDD is automatically cancelled, so that all the data in the HDD are invalidated. Thus, even though the HDD is stolen and the like, the leakage of the data cannot occur.
However, if the HDD connected with the machine is replaced with a HDD without the authentication function, after the data are written in the HDD, the HDD is issued externally, and the written-in data will be issued outside.